Some types of solid state non-volatile memory, such as flash memory, record binary data by storing a certain amount of electrical charge in a memory cell. When the data is read from one of these charge-based non-volatile memories, the voltage level of the stored charge is compared to a reference voltage. The binary value of the data read from that cell depends on whether the voltage of the stored charge is higher or lower than the reference voltage. However, since the stored charge is an analog phenomenon, its actual value may not be exactly what was intended, and errors may be encountered when the data is read. Error correcting code (ECC) units may be used to detect and correct some of these errors, but sometimes the errors are too numerous to all be corrected in this manner. When this happens, the data may be permanently lost.